1. Field of the Invention
The present invention relates generally to the field of rotary coupling systems for mechanical power transmission. More particularly, the invention relates to an innovative technique for locating and securing a shaft with respect to a mating sleeve. The invention is particularly applicable to shaft or sleeve-supported structures, such as gear reducers and the like.
2. Description of the Related Art
Various arrangements have been proposed and are currently in use for connecting rotating machine elements to one another. In general, such arrangements enable rotating elements, such as shafts, sleeves, bushings and so forth to be coaxially aligned with one another and secured to one another in such a way as to transmit mechanical power between the coupled elements. Certain industrial applications require the coupling of a rotating shaft with a sleeve adapted to fit partially or entirely over the shaft. For example, in one such application, a gear reducer is hung from and supported by an output shaft, itself part of a machine drive system. In such applications, not only must the coupling system support torques transmitted between the rotating elements, but must also solidly fix the shaft and sleeve combination so as to support bending moments exerted by the overhung load.
Various locking structures have been devised for coupling shafts to sleeves, particularly for use with overhung loads such as shaft-mounted gear reducers. A number of these arrangements incorporate various wedge-type inserts that fit between the sleeve or hub and the shaft. The insert, typically formed as a frustoconical bushing, is inserted at an end of the sleeve. An annular flange bounds the base of the frustoconical element for facilitating its insertion and removal. In certain known arrangements, an annular flange of this type includes apertures for receiving fasteners. The fasteners are drawn toward the sleeve or hub by means of a cooperating annular flange fixed to the sleeve. Thus, by tightening the fasteners, the frustoconical element is forced into the sleeve. A tapered inner surface of the sleeve cooperates with a correspondingly tapered outer surface of the frustoconical element to drive the inner wall of the frustoconical element snugly against the shaft when the arrangement is assembled and the frustoconical element is wedged into place. An arrangement generally of this type is described in U.S. Pat. No. 4,626,114, issued to Phillips on Dec. 2, 1986.
While such arrangements provide solid attachment between hubs and shafts, they are limited in several important ways. For example, in the arrangement described above, the inner face of the sleeve or hub is typically an integral element of a gear reducer or other machine, and must be machined or otherwise profiled to provide the proper tapered surface against which the frustoconical element is brought to bear. The sleeve is therefore designed specifically to interface with a particular coupling system, reducing its universality for various applications. A system generally of this type is described in U.S. Pat. No. 3,590,652, issued to Strang on Jul. 6, 1971. Moreover, in certain applications, it is useful to employ a single long, tapered bushing, while in other arrangements a pair of shorter bushings on either end of the sleeve is more advantageous. The latter arrangement is particularly useful for shafts of considerable length, extending through or nearly through the entire sleeve. However, systems of the type described above generally are not well suited to the use of either a pair of bushings (i.e., one on either side of a sleeve) or a single long bushing (i.e., inserted into one end of the sleeve).
Other systems have been devised for interfacing sleeves having substantially cylindrical inner surfaces with shafts. In one such arrangement, an annular groove is formed within the sleeve for receiving an abutment ring. The ring is installed in the groove and serves as a backup member for a wedge-type bushing which is received within the sleeve bore. An interfacing wedge insert is then positioned between the inner bushing and the shaft. An annular flange on the insert receives fasteners for drawing the insert toward the sleeve, thereby locking the shaft and sleeve with respect to one another by the intermediary of the bushing and insert. While this system provides excellent torque transmission capabilities and supports heavy loads in a relatively universal arrangement, it too is not without drawbacks. For example, it has been found the placement of a snap-type backup ring in a groove formed deep within a sleeve can be difficult, particularly on larger machinery requiring robust backup rings. Moreover, in certain circumstances, the inner wedge-shaped bushing may become fixed between the tapered insert and the inner surface of the sleeve without initially abutting the backup ring. During subsequent use, the bushing may shift within the bore (e.g. towards the backup ring) loosening the coupling between the shaft and sleeve.
There is a need, therefore, for an improved shaft/sleeve coupling arrangement which does not suffer from the drawbacks of existing systems of the types described above. In particular, there is a need for an arrangement which can be easily installed and which remains effective at transmitting even substantial loads between driving and driven elements during use. Moreover, there is a need for a system that can be disassembled as needed and that offers the possibility of incorporating long and short tapered inserts in various combinations in a generally universal coupling system.